The present invention relates to a polymer battery module packaging material having satisfactory moistureproof capability and resistant to chemicals, and a method of manufacturing such a polymer battery module packaging material.
A polymer battery, which is also known as a lithium secondary battery, has a polyelectrolyte, and positive and negative electrodes formed of active polymers.
The polymer battery (lithium secondary battery) comprises a lithium battery module having a positive electrode collector (aluminum or nickel), a positive electrode active substance layer (metal oxide, carbon black, a metal sulfide, an electrolytic solution or a polymer, such as polyacrylonitrile), an electrolytic layer (an electrolytic solution of propylene carbonate, ethylene carbonate, dimethyl carbonate or ethylene methyl carbonate, an inorganic solid electrolyte of a lithium salt or a gelled electrolyte), a negative electrode active layer (lithium, an alloy, carbon, a liquid electrolyte or a polymer, such as polyacrylonitrile) and a negative collector (copper, nickel or a stainless steel), and a package containing the lithium battery module therein.
The polymer battery is used as a power supply for personal computers, portable terminal devices, such as portable telephones and PDAs, video cameras, electric vehicles, robots, artificial satellites and the like, and as an energy storage battery.
The package of the polymer battery is a cylindrical or parallelepipedic metal can formed by pressing a metal sheet or a pouch formed by working a packaging laminated structure consisting of a base layer, an aluminum layer and a sealant layer.
Packages for polymer batteries have the following problems. The metal can has rigid walls and hence the shape of the battery is dependent on that of the metal can. Since the hardware is designed so as to conform to the shape of the battery, the dimensions of the hardware are dependent on the shape of the battery, which reduces the degree of freedom of designing the shape of the hardware.
A pouch made from a packaging laminated structure for holding a polymer battery therein or an embossed package provided with a hollow for holding a polymer battery therein and formed by pressing a packaging laminated structure has been developed. The embossed package, as compared with a pouch, is compact. Moistureproof capability, piercing strength and insulating property are requisite properties of packages for polymer batteries.
A packaging laminated structure consisting of a base layer, a barrier layer and a heat-sealable layer has been proposed as a packaging material for forming a polymer battery package. It is confirmed that adhesive strength between the layers of the packaging laminated structure affects the requisite properties of a polymer battery package. If adhesive strength between the barrier layer and the heat-sealable layer is insufficient, external moisture penetrates the packaging laminated structure forming a polymer battery package into the polymer battery package, the electrolyte of the polymer battery module reacts with the moisture to produce hydrofluoric acid. The hydrofluoric acid thus produced corrodes the surface of the aluminum layer to cause the delamination of the barrier layer and the heat-sealable layer. An embossed package formed by pressing a packaging laminated structure has a hollow. Sometimes the base layer and the barrier layer of the packaging laminated structure are delaminated when forming the hollow by pressing.
The inventors proved through studies that the adhesive strength between the component layers of a packaging laminated structure can be improved by forming an acid-denatured polypropylene film on a surface of an aluminum layer by a process of applying an emulsion of an acid-denatured polypropylene resin to a surface of the aluminum layer in a film and baking the film, and forming a packaging laminated structure of an adhesive resin layer of an acid-denatured polypropylene resin and a heat-sealable layer of a polypropylene resin by co-extrusion. However, the formation of the acid-denatured polypropylene film by baking takes much time and the packaging laminated structure cannot be produced at a satisfactory production efficiency.
When embossing the packaging laminated structure, friction between an embossing male die and the heat-sealable layer is large, the heat-sealable layer is whitened or fine cracks are formed in the heat-sealable layer, the forming stability is unsatisfactory and, sometimes, cracks and creases are formed when the heat-sealable layer of the packaging laminated structure is formed of a random polypropylene resin.
It is an object of the present invention to provide a polymer battery module packaging material excellent in moistureproof capability and resistance to chemicals, and a method of manufacturing such a polymer battery module packaging material.
According to the present invention, a polymer battery module packaging material includes a base layer, a barrier layer, a chemically converted layer, a heat-sealable layer, and a liquid paraffin layer, wherein the heat-sealable layer is formed of a polyolefin resin.
In the polymer battery module packaging material according to the present invention, the chemically converted layer is formed by a phosphate chromate treatment.
In the polymer battery module packaging material according to the present invention, the heat-sealable layer is formed of a random polypropylene resin.
In the polymer battery module packaging material according to the present invention, the heat-sealable layer is formed of a linear low-density polyethylene resin.
According to the present invention, a polymer battery module packaging material includes a base layer, a barrier layer, a chemically converted layer and a heat-sealable layer, wherein the heat-sealable layer is formed of a thermoplastic resin containing 0.5% to 20% by weight of an additive, the additive is one or some of liquid paraffins, fatty ester lubricants, polyester dispersants, polyglycerol ester additives.
In the polymer battery module packaging material according to the present invention, the chemically converted layer is formed by a phosphate chromate treatment.
In the polymer battery module packaging material according to the present invention, the thermoplastic resin forming the heat-sealable layer is a random propylene resin.
In the polymer battery module packaging material according to the present invention, the thermoplastic resin forming the heat-sealable layer is a linear low-density polyethylene resin.
In the polymer battery module packaging material according to the present invention, the thermoplastic resin forming the heat-sealable layer is a medium-density polyethylene resin.
In the polymer battery module packaging material according to the present invention, the heat-sealable layer is a multilayer structure consisting of two or more layers, and at least the innermost layer of the multilayer structure contains the additive.
According to the present invention, a polymer battery module packaging material manufacturing method includes the steps of processing at least one of the surfaces of a barrier layer by a chemical conversion treatment, laminating a base layer to one of the surfaces of the barrier layer by a dry-lamination process, forming a packaging laminated structure by forming a heat-sealable layer of a random polypropylene resin on the other surface processed by the chemical conversion treatment of the barrier layer by a dry-lamination process, and coating a surface of the heat-sealable layer of the random polypropylene resin with a liquid paraffin.
In the polymer battery module packaging material manufacturing method according to the present invention, both the surfaces of the barrier layer are processed by the chemical conversion treatment.
According to the present invention, a polymer battery module packaging material manufacturing method includes the steps of processing at least one of the surfaces of a barrier layer by a chemical conversion treatment, laminating a base layer to one of the surfaces of the barrier layer by a dry-lamination process, forming a packaging laminated structure by forming a heat-sealable layer by bonding a random polypropylene resin film to the other surface processed by the chemical conversion treatment of the barrier layer with an adhesive resin layer of an acid-denatured polypropylene resin, heating the packaging laminated structure at a temperature not lower than the softening point of the acid-denatured polyolefin resin, and coating a surface of the heat-sealable layer of the random polypropylene resin with a liquid paraffin.
In the polymer battery module packaging material manufacturing method according to the present invention, both the surfaces of the barrier layer are processed by the chemical conversion treatment.
In the polymer battery module packaging material manufacturing method according to the present invention, the heat-sealable layer is bonded to barrier layer with the adhesive resin layer by a sandwich-lamination process.
In the polymer battery module packaging material manufacturing method according to the present invention, the heat-sealable layer is bonded to an aluminum layer with the adhesive resin layer by a coextrusion-lamination process.
In the polymer battery module packaging material manufacturing method according to the present invention, the steps of coating the heat-sealable layer with the liquid paraffin and heating the packaging laminated structure are in-line processes.
In the polymer battery module packaging material manufacturing method according to the present invention, the step of coating the heat-sealable layer with the liquid paraffin is a discrete step to be carried out after the step of heating the packaging laminated structure.
According to the present invention, a polymer battery module packaging material manufacturing method includes the steps of processing at least one of the surfaces of a barrier layer by a chemical conversion treatment, laminating a base layer to one of the surfaces of the barrier layer by a dry-lamination process, forming a packaging laminated structure by heating the other surface processed by the chemical conversion treatment of the barrier layer at a temperature not lower than the softening point of an acid-denatured polypropylene resin and bonding a heat-sealable layer of a random polypropylene resin film to the other surface processed by the chemical conversion treatment of the barrier layer with an adhesive resin layer of the acid-denatured polypropylene resin, and coating a surface of the heat-sealable layer of the random polypropylene resin with a liquid paraffin.
In the polymer battery module packaging material manufacturing method according to the present invention, both the surfaces of the barrier layer are processed by the chemical conversion treatment.
In the polymer battery module packaging material manufacturing method according to the present invention, the adhesive resin layer and the heat-sealable layer are formed on the barrier layer by a sandwich-lamination process.
In the polymer battery module packaging material manufacturing method according to the present invention, the adhesive resin layer and the heat-sealable layer are formed on the barrier layer by a coextrusion-lamination process.
In the polymer battery module packaging material manufacturing method according to the present invention, the steps of coating the surface of the heat-sealable layer with the liquid paraffin and heating the packaging laminated structure are in-line processes.
In the polymer battery module packaging material manufacturing method according to the present invention, the step of coating the heat-sealable layer with the liquid paraffin is a discrete step to be carried out after the step of heating the packaging laminated structure.
According to the present invention, a polymer battery module packaging material manufacturing method includes the steps of processing at least one of the surfaces of a barrier layer by a chemical conversion treatment, laminating a base layer to one of the surfaces of the barrier layer by a dry-lamination process, forming a packaging laminated structure by forming a heat-sealable layer by bonding a film of a linear low-density polyethylene resin to the other surface processed by the chemical conversion treatment of the barrier layer with an adhesive resin layer of an acid-denatured linear low-density polyethylene resin by a sandwich-lamination process, heating the packaging laminated structure at a temperature not lower than the softening point of the acid-denatured linear low-density polyethylene resin, and coating a surface of the heat-sealable layer of the linear low-density polyethylene resin with a liquid paraffin.
In the polymer battery module packaging material manufacturing method according to the present invention, both the surfaces of the barrier layer are processed by the chemical conversion treatment.
According to the present invention, a polymer battery module packaging material manufacturing method includes the steps of processing at least one of the surfaces of a barrier layer by a chemical conversion treatment, laminating a base layer to one of the surfaces of the barrier layer by a dry-lamination process, forming a packaging laminated structure by forming a layer of an acid-denatured polypropylene resin and a film of a random polypropylene resin on the other surface processed by the chemical conversion treatment of the barrier layer by a thermal-lamination process, and coating a surface of the film of the random polypropylene resin of the packaging laminated structure with a liquid paraffin.
In the polymer battery module packaging material manufacturing method according to the present invention, both the surfaces of the barrier layer are processed by the chemical conversion treatment.